1. Field of the Invention
This invention relates to a band conveying device for use with a tire forming machine.
2. Description of the Prior Art
The present applicant filed Japanese Patent Application No. 63-82989, which discloses a tire conveying device and proposes to attract a member to be conveyed by vacuum, does not teach vacuum attraction being performed with respect to any surface portion of the member to be conveyed except a joint portion.
In the process of forming a tire, a band is formed by winding a belt-shaped material around a cylindrical drum.
A so-called vacuum attractor (vacuum pad) is effective in attracting a smooth surface, but not a rough surface having a stepped portion. The reason is that the vacuum attractor cannot fit with the stepped surface portion of the member to be attracted, thus leaving a gap between them so that air is sucked through the gap, disabling vacuum attraction. Since a plurality of vacuum attractors are usually connected together by one pipeline, if at least one vacuum attractor becomes disabled, the others cannot get a sufficient vacuum and attain their function.
When the belt-shaped material is wound around the drum in a tire forming machine, each resulting joined portion of the material causes roughness in the form of a stepped portion. Since the position of such a stepped portion can be detected, it is possible to position the vacuum attractors so as not to avoid the stepped portion. However, the belt-shaped material is usually formed by joining a plurality of material segments of a given length, and each resulting joined portion causes roughness in the form of another stepped portion. Such another stepped portion can hardly be detected by the forming machine. Even if this second type of stepped portion can be detected, it is very difficult to position the vacuum attractors so as not to confront the two types of stepped portions. Consequently, the band cannot be conveyed reliably.